The first meetings between Sounders FC and Real Salt Lake started off simple enough. In 2009 after Seattle joined MLS, the two sides traded home victories without much incident.

In 2010, a pair of hotly contested draws spiced up the schedule for future matches and in 2011 it boiled over into a full-blown rivalry. Both teams have kept their core intact through the five years of battles and on Friday they will meet for the 17th time in all competitions with many of those pieces at play.

They both know the feeling of the other ending their respective seasons, as RSL eliminated Seattle from the 2011 MLS Cup Playoffs and Sounders FC returned the favor in 2012.

“When you have a series of games and the playoffs and they’ve knocked us out of the playoffs and we’ve knocked them out of the playoffs, that rivalry grows a little bit from there,” Sounders FC Head Coach Sigi Schmid said. “We knocked them off at home when they had a long unbeaten streak. That didn’t sit well with them. All of those little games add up.”

Players from Seattle remember Alvaro Saborio’s stoppage-time equalizer in 2010 at Rio Tinto Stadium just as RSL recalls Lamar Neagle’s cracker of a goal the following year to halt Salt Lake’s 29-match home unbeaten streak.

Meanwhile, both sides know the value of the league’s top holding midfielders in Seattle’s Osvaldo Alonso and RSL’s Kyle Beckerman, and the importance of cold-blooded goalkeepers Michael Gspurning and Nick Rimando.

Just as the regional derbies with Vancouver Whitecaps FC and the Portland Timbers have blossomed in the last three years, so has the competitive strife between Seattle and Salt Lake, two of the top three teams in MLS over the last five seasons.

“If we are playing against them, there is always something to play for and that makes it very special,” Gspurning said. “The games are good. The games are tough for both teams. That makes it very interesting for spectators. Portland and Vancouver are big rivals, but games against Salt Lake are always dramatic.”

This time around, both teams are coming into the match riding hot streaks. Salt Lake has won its last two matches 4-2 over the Timbers and 4-0 against the Columbus Crew to get ahold of the top spot in the MLS standings at 14-8-6. Seattle, meanwhile, is on a four-game winning streak, coming out victorious in seven of its last eight matches to jump to second while still toting games in hand at 14-8-4.

Both are also battling with injuries and integrating players returning from international duty.

For Seattle, Eddie Johnson and Clint Dempsey both saw lengthy playing time in a 2-0 win for the U.S. National Team over Mexico in Columbus on Tuesday. Brad Evans is also working his way back from a calf strain while Shalrie Joseph is out with a sprained knee.

Saborio was called in for Costa Rica, but was limited in its 3-1 win over the U.S. on Friday and then was sent back to Salt Lake City to treat a calf strain, putting his availability this week into question.

However, RSL’s success with Saborio in the starting lineup isn’t as good as his 10 goals in 13 matches would imply. In his 12 starts, Salt Lake is just 5-4-3. While that is a respectable 1.5 points per match, RSL averages 1.88 points per match at 9-4-3 when he doesn’t start.

Far more critical to its success is Beckerman. The longtime RSL captain played a grueling 90 minutes for the U.S. National Team on Tuesday. In the seven matches Beckerman hasn’t started this season, RSL is just 2-3-2.

While Friday’s matchup is the last between the two clubs on the schedule, Gspurning, for one, anticipates another playoff encounter, as they seem destined for another postseason clash.

“I think there’s a pretty high chance, yeah,” he said. “I would bet on it, if I had to.”